Snake Care Tip: Cover the Screen Lid of a Glass Cage

Lately, I’ve been getting a lot of correspondence from snake keepers who are having trouble maintaining temperatures inside a glass terrarium. In this context, I’m talking about the type of glass tank that has a screen lid on the top. Your basic all-glass terrarium used for reptiles and small animals.

These enclosures can cause all sorts of problems when used to house reptiles. Heat, humidity and exposure are the most common problems. In this snake care lesson, I’ll offer some tips for controlling the temps inside one of these screen-lid-style enclosures.

Here’s an email I received last week: “I am keeping a ball python in a 40-gallon glass tank that I purchased from Petco. It has a screen lid that snaps onto the top. The cage is getting too cool at night, down to 70 degrees. I have a 150-watt heat lamp on top of the cage right now. What can I do to increase the nighttime temps inside my ball python’s enclosure?” Here’s what I usually tell people:

Cover the Lid, or Use an Under-Tank Reptile Heat Mat

It’s one of the most common cage setups for pet snakes. The animal is placed inside of a glass tank / terrarium with a screen lid covering the top. Then, a heat lamp is placed on top of the screen lid, toward one end of the cage. This is done to create a basking spot for the ectothermic inhabitant.

Like all pet snakes, ball pythons need a proper temperature gradient in their cages

In theory, this kind of setup makes a lot of sense. The lamp will warm one end of the snake’s cage, thereby creating a thermal gradient (which means that one end is warmer than the other). This allows the pet snake to thermoregulate, or move between the two zones to regulate its body temperature as it would in nature. It’s all perfectly logical.

It’s true that snakes need a thermal gradient. You don’t want the entire cage to be the same temperature. This can lead to all sorts of health problems for a captive reptile. You want to create a range of temps by making one end of the enclosure warmer than the other end.

The problem is that heat rises. That’s why the upstairs of my house is always warmer than the downstairs. And that’s why hot air balloons go up when filled with hot air. You learned this in science class.

Unless it’s a green tree python or some other arboreal species, your pet snake will spend most of its time on the bottom of the cage. But the heat source in the scenario I just described sits on the top of the cage. The heat starts off above the snake, and the natural tendency is for it to rise. Clearly, you can see the problem with this kind of cage setup. With a screen lid covering the top of the glass cage, there is nothing to keep the warm air from rising up and out of the snake’s enclosure. Goodbye ideal temperatures. Hello health problems.

I have a plastic reptile enclosure with a heat lamp mounted in the top. But the lamp sits deep inside a recessed area built into the top of the cage. The recessed area has an aluminum grate to prevent the snake from burning itself on the bulb. In this scenario, the heat from the lamp radiates into the cage, where much of it is retained by the plastic top and sides of the snake’s enclosure. Aside from the small area where the lamp sits, the rest of the cage top is solid.

If you have a screen lid on top of a terrarium, and you’re having troubling keep the cage warm enough for your pet snake, you basically have two choices:

You could cover part of the screen lid to reduce the amount of warm air that escapes. Or…

You could place the heat source below the reptile enclosure, using reptile heating mats or pads. Flexwatt tape is another way to achieve this effect.

You might even have to do both of these things, depending on the average temperatures in the room where the cage is located. By placing the device beneath the enclosure, your pet reptile will get more of the warmth that rises up from the bottom of the cage. This if often referred to as “belly heat,” since the animal warms itself belly first. Of course, it’s more than just surface heat. It will radiate upward to fill the rest of the cage as well.

How much warmth is actually retained in this scenario will depend on the type of lid. A screen lid will still allow much of it to escape, though it’s still a better scenario than having the lamp on top of the screen lid.

Safety Note: Use common sense. Practice fire safety. Make sure you don’t place any flammable materials in contact with a reptile heat lamp. Don’t overload your electrical outlets. You know the rest.

Temperature: A Critical Aspect of Snake Care

This is not a subject to take lightly. You need to ensure your pet snake has proper temperatures inside its cage at all times. Nothing is more detrimental to a reptile’s health than a cage that’s too cool. The same goes for the other end of the spectrum. A cage that gets too hot is just as dangerous.

Reptiles cannot warm their bodies internally like we can. Nor can they cool down by panting or sweating, the way mammals do. They are extremely sensitive to their environmental conditions. A pet snake will rely on its environment to regulate its body temperature. This means it will rely on you to provide such conditions.

Do you have questions about keeping snakes as pets, or some other aspect of reptile care? Head on over to Reptasia.com and post your question in our forums. I’ll see you there!

16 thoughts on “Snake Care Tip: Cover the Screen Lid of a Glass Cage”

What do you suggest covering the screen with. I have both a heat pad under and a top light. Recently covered with plexi glass and magnetic heat covers that go over floor house heat grates but still not fixing issue.

A lot of materials can be used, as long as they don’t come in contact with a heating lamp or ceramic unit (which could be a fire hazard). Look around the house. Be creative. Once, I cut the front and back covers off a three-ring binder, because they were the perfect size to cover a portion of my screen lid. Sometimes just covering one-third or a half of the lid can make a difference. Without some kind of covering, the heat just rises right out of those types of cages. It doesn’t get retained very well.

We just got our first ball python and tank — with screen cover — today. It is (shockingly) having trouble maintaining the proper temp, seems to be hanging out at 83-87 on the warm end, and 73 at the cold end. I put some batting left over from an old quilting project over the top to get it there, but I’m not sure that it is enough. Do you recommend switching to another top, and if so, what?

Hi Emma. In the short term, you might want to find some kind of material (like plastic) that sits flush over part of the lid, or most of the lid. The front and back covers from three-ring binders can be used for this purpose, if you cut them off. Your local hardware store might have something even better. Long term, you might want to consider using a more enclosed habitat for your ball python, like a Vision cage, Animal Plastics, or something similar. Glass terrariums with screen lids can be problematic when it comes to heat retention, as you’ve discovered.

I thought having the heater on the side would help create a thermal gradient. I put a towel over the cool side of the cage, and that helped get the temperature up, but I don’t feel comfortable putting a towel under the heat lamp. The temperature and humidity are fine with the towel, though it drops a couple of degrees at night. Thanks for the article Brandon!

I have a 2 month old red tail boa in a 20L tank. I have a heating pad under and heat lamp. 75 watt bulb and can’t get the heat in the hot side over 75. I have also duct taped half of the screen top and humidity stays just at 60 unless I spray then it goes up but comes back down. Help please

Hi so I’m having a difficult time getting the enclosure to the correct temp. You recommend aluminum foil, but I have a heat mat under and a 50watt heat lamp. How can I use foil with that? Also on the other side I have the daylight lamp. Please help.

Hello. I have 2 10 year old females.
Both sand boas. Adopted them both the beginning of may. Fed them both f/t mice no issues eating. Moved them from a 30 low to a 55 long. Have heat mat and ceramic and red heat lamps on top.
One boa eats every 2 weeks. The other hasn’t eaten in 2 months.
Help!!